Yeah, in my experience I've found that there's really no point to investing in Detection if you aren't already playing stealthily yourself.
Plus, it only takes me a couple of runs through an area to memorize all of the enemy locations, at which point Detection is even more useless because I can just throw a grenade or a fireball where I already know they're going to be. The main holes in this tactic are the Faceless Gaunts in Deep Caverns, which patrol in very... unusual ways (and, seemingly, love to hide in corners).
Detection still helps you with uncovering traps and mines, though, right? There's still a lot of use in that (if you haven't memorized where they are, too, of course).